Generally, deformation of a wood material serving as furniture materials or building materials, such as distortion or warpage, is generated by contraction thereof. The constriction of the wood material differs according to species, age and trimming season of tree for the wood material and grain of the wood. The contraction percentage of the wood material is generally increased in order of a direction of fibers, a radius direction and a direction of age (annual ring or grain).
After trimming and sawing, wood material is dried for a designated period of time and is then processed to make products. The drying of the wood material protects the wood material from corrosion by bacterium and damage from insects, prevents damage, contraction and cracks thereof, improves strength and endurance thereof, and facilitates reduction in weight, coating and chemical treatment.
Mainly, conventional billiard cues have been made of hard maple. Instead of such a natural wood material, conventional billiard cues have been made of metal, such as aluminum, FRP, used as a material for fishing rods, or carbon fiber. The above materials have striking sensibility lower than that of the wood material, and generate the movement of the billiard cue in striking, thereby being incapable of absorbing impact in striking so that the impact is transmitted to a user's hand, thus being unsuitable for high-quality and popularization of the billiard cues.
For example, Korean Utility Model Registration No. 164192 discloses a billiard cue made of a wood material and a glass fiber pipe. The billiard cue comprises a shaft made of the wood material, including a handgrip portion and a strike portion, a glass fiber or carbon fiber pipe connected to the upper end of the shaft for preventing the warpage of the shaft, and a coating layer coating the pipe for protecting the pipe from external environmental stresses. Further, Korean Patent Laid-open No. 87-4717 discloses a method for manufacturing a billiard cue using a glass fiber pipe, Korean Utility Model Laid-open No. 86-11554 discloses a billiard cue manufactured by bonding and pressing rectangular pieces, cleaved from a material wood, to a conventional veneer board such that they cross each other and provided with a reinforcing plastic inserted into the central portion thereof, and Korean Utility Model Laid-open No. 84-4796 discloses a billiard cue manufactured by stacking four to eight layers of a thin plate material, which are infiltrated with carbolic acid resin at a high temperature, in a high-temperature and high-pressure state.
As time goes by, the billiard cues made of the wood material cannot maintain their straight states and are warped due to the contracting force of the wood material thereof, thereby being disadvantageous in that they cannot strike a correct point of a billiard ball and cannot provide desirable striking force or rotating force to the billiard ball.
In order to solve the warpage of the wood billiard cue, there was developed a billiard cue, which is manufactured by sawing straight lumber into a plurality of pieces having a triangular section, bonding the plural pieces in a radial shape, and machining the bonded unit using a lathe, as shown in FIG. 6. In case that the above billiard cue is used, a central portion of the billiard cue, which is not strong, depreciates striking force and striking sensibility, thereby causing general persons as well as pro billiard players to be reluctant to use the above billiard cue. Further, it is difficult to form an external or internal screw unit on the central portion (in case of an assembled cue), or to process the front end of the cue for attaching a tip thereto. Further, although the front end of the cue is processed, the processed end of the cue is easily damaged by impact.